Sorry Cap'n - most of what you say is not what I have found when listening (also been around for over 40 years).
Can't answer in full just now, but can we just clear up one point.
"a good proportion of those songs in a traditional singers repertoire were originally broadsheets"
If you know this for certain, you have information the rest of us don't have access to.
We do not know for certain that ANY traditional song originated on a broadside; some have suggested that they might have, but we have no way at all of knowing where our songs originated (except those that bear a writers name).
Jim Carroll